U.S. patent application number 13/858815 was filed with the patent office on 2014-10-09 for directional based audio response to an external environment emergency signal.
This patent application is currently assigned to DTS, Inc.. The applicant listed for this patent is DTS, INC.. Invention is credited to Shankar Rathoud, Cedric Tio, Liang (Vincent) Wang, Christopher Yap.
Application Number | 20140301556 13/858815 |
Document ID | / |
Family ID | 51654479 |
Filed Date | 2014-10-09 |
United States Patent
Application |
20140301556 |
Kind Code |
A1 |
Wang; Liang (Vincent) ; et
al. |
October 9, 2014 |
DIRECTIONAL BASED AUDIO RESPONSE TO AN EXTERNAL ENVIRONMENT
EMERGENCY SIGNAL
Abstract
An audio signal attenuation system and method for detecting an
audio emergency warning signal (or alarm) in a vehicle in which an
audio signal is being played. Embodiments of the system and method
make it easier for a police, fire, or other emergency alarm or
siren to be heard in a loud or noisy listening environment when
audio signal is being reproduced. This is achieved using selective
frequency attenuation, which identifies a frequency of the alarm
and then selectively attenuates the alarm frequency in the audio
signal. Moreover, direction data that includes information about
from which direction the alarm is coming can be used to selectively
attenuate the alarm frequency in certain channels (or speakers) of
the audio signal. In some embodiments, audio cues are used to alert
the listener to the alarm signal and are adjusted based on alarm
distance from the vehicle, speed, and the type of alarm.
Inventors: |
Wang; Liang (Vincent);
(Singapore, SG) ; Yap; Christopher; (Singapore,
SG) ; Rathoud; Shankar; (Singapore, SG) ; Tio;
Cedric; (Singapore, SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DTS, INC. |
Calabasas |
CA |
US |
|
|
Assignee: |
DTS, Inc.
Calabasas
CA
|
Family ID: |
51654479 |
Appl. No.: |
13/858815 |
Filed: |
April 8, 2013 |
Current U.S.
Class: |
381/57 |
Current CPC
Class: |
H03G 9/00 20130101; H03G
9/005 20130101; H03G 9/025 20130101 |
Class at
Publication: |
381/57 |
International
Class: |
H03G 9/00 20060101
H03G009/00 |
Claims
1. A method for processing an audio signal, comprising selectively
attenuating a specific frequency in the audio signal, the specific
frequency corresponding to an alarm frequency of an audio emergency
warning signal, so that an amplitude of the alarm frequency in the
audio signal is attenuated relative to other frequencies in the
audio signal.
2. The method of claim 1, further comprising removing the alarm
frequency from the audio signal by attenuating the amplitude of the
alarm frequency to zero in the audio signal.
3. The method of claim 1, further comprising selectively
attenuating the alarm frequency for each channel of the audio
signal.
4. The method of claim 3, further comprising attenuating a
low-frequency effects channel of the audio signal to allow a
listener to hear the audio emergency warning signal.
5. The method of claim 3, further comprising attenuating front
channels of the audio signal more than other channels of the audio
signal to allow a listener to hear the audio emergency warning
signal.
6. The method of claim 1, wherein the audio emergency warning
signal is external to a listening environment of the audio
signal.
7. The method of claim 1, further comprising: analyzing the audio
emergency warning signal to obtain alarm frequency characteristics;
and deriving a filter from the alarm frequency characteristics.
8. The method of claim 7, further comprising filtering the alarm
frequency from the audio signal using the filter derived from the
alarm frequency characteristics to selectively attenuate the alarm
frequency in the audio signal.
9. The method of claim 1, further comprising: converting the audio
emergency warning signal into a frequency domain; comparing the
alarm frequency characteristics to a set threshold; and computing a
fundamental frequency of dominant peaks of the audio emergency
warning signal that are above the set threshold, wherein the
fundamental frequency corresponds to the alarm frequency.
10. A method for processing an audio signal having a plurality of
channels, comprising selectively attenuating an amplitude of at
least some of the plurality of channels based on a direction of an
audio emergency warning signal that is external to a listening
environment of the audio signal.
11. The method of claim 10, further comprising detecting a
direction relative to the vehicle from which the audio emergency
warning signal is being emitted to generate direction data.
12. The method of claim 11, further comprising: processing the
direction data to determine an amplitude of the audio emergency
warning signal as a function of direction; and selectively
attenuating the amplitude of at least some of the plurality of
channels based on the amplitude of the audio emergency warning
signal as a function of direction.
13. The method of claim 11, further comprising: analyzing the
direction data to determine scale factors for scaling the amplitude
of at least some of the plurality of channels based on the
direction relative to the vehicle from which the audio emergency
warning signal is being emitted; and selectively attenuating the
amplitude of at least some of the plurality of channels using the
scale factors.
14. The method of claim 13, further comprising: analyzing the audio
emergency warning signal to obtain alarm frequency characteristics;
deriving a filter from the alarm frequency characteristics that
filters an alarm frequency of the audio emergency warning signal
from the audio signal; and filtering the audio signal using the
filter and the scale factors to selectively attenuate the alarm
frequency in the audio signal in at least some of the plurality of
channels.
15. The method of claim 14, further comprising scaling the
amplitude of at least some of the plurality of channels such that
channels in the direction relative to the vehicle from which the
audio emergency warning signal is being emitted are scaled to a
lower amplitude than other channels.
16. A method for detecting an audio emergency warning signal in a
vehicle in which an audio signal is being played back, comprising:
determining an overall power level of the audio signal; determining
an alarm frequency of the audio emergency warning signal that
represents a fundamental frequency of the audio emergency warning
signal; determining a direction relative to the vehicle from which
the audio emergency warning signal is being emitted to obtain
direction data, the audio emergency warning signal emanating from a
source external to the vehicle; computing multi-channel attenuation
coefficients from the overall power level, alarm frequency, and
direction data; and selectively attenuating an amplitude of at
least some of channels of the audio signal based on the
multi-channel attenuation coefficients to detect the audio
emergency warning signal from within the vehicle.
17. The method of claim 16, further comprising: generating a filter
using the multi-channel attenuation coefficients; and filtering the
audio signal using the filter to attenuate the alarm frequency in
the audio signal.
18. The method of claim 17, further comprising: determining scale
factors using the direction data; and scaling an amplitude of at
least some of the channels of the audio signal using the scale
factors.
19. The method of claim 16, further comprising playing the audio
emergency warning signal through at least some of the plurality of
channels based on the direction data such that the audio emergency
warning signal is played through channels corresponding to the
direction relative to the vehicle from which the audio emergency
warning signal is being emitted.
20. The method of claim 16, further comprising playing audio cues
through the plurality of channels to notify a listener of the audio
emergency warning signal.
Description
RELATED APPLICATION
[0001] This application is a non-provisional of U.S. Provisional
No. 61/621,915, filed Apr. 9, 2012, the disclosure of which is
hereby incorporated by reference in its entirety.
BACKGROUND
[0002] The demand for improved audio and video entertainment has
moved beyond the home and is now prevalent in the automotive space.
New entertainment systems are one of the hottest trends in the
automotive marketplace. Automotive entertainment systems have
become as sophisticated as home theater systems. Consequently,
automobile occupants have access to rich sounding audio and
Internet-based applications through complex entertainment systems.
Moreover, engineering and material improvements make the automobile
cabin fairly insulated from external sounds such as road noise.
[0003] Sophisticated audio systems of the automotive entertainment
systems provide high-quality audio that can be enjoyed occupants in
the relatively quiet environment of the automobile cabin. However,
these same enhancements to audio enjoyment in an automobile also
prevent a driver from hearing noises external to the car. While
some of these noises may be insignificant environment noise, others
may include important emergency signals that a driver should be
able to detect and respond accordingly. Thus, drivers are becoming
increasingly unable when driving to readily detect and adapt to
external warning signals--such as fire, police, or medical sirens
and alarms.
SUMMARY
[0004] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter.
[0005] In general, embodiments of the audio signal attenuation
system and method are used to process an audio signal in response
to an external alarm (also called an audio emergency warning
signal). This audio emergency warning signal may be a siren being
emitted from an emergency vehicle, such as a fire, medical, or
police siren. Embodiments of the system and method make it easier
for the audio emergency warning signal to be detected in a loud or
noisy listening environment where the audio signal is being
reproduced. In some embodiments the listening environment is a
mobile listening environment, such as the interior of a vehicle
(such as an automobile). For example, in some embodiments the
listening environment may be an automobile and the audio signal may
be music playing from a stereo system in the automobile. The system
and method may it possible for a listener in the automobile to hear
an alarm signal that is outside of the automobile, even when the
music is playing loud and the windows are up.
[0006] In some embodiments of the system and method, the audio
emergency warning signal is detected and its frequency
characteristics are determined. In particular, an alarm frequency
of the alarm is determined and that particular frequency is
filtered from the audio signal. This filtering may include complete
removal from the audio signal or may be a distinct attenuation of
the audio signal such that the alarm signal can be heard by the
listener. There is a distinct advantage is performed selective
frequency attenuation instead of channel volume attenuation. In
order to achieve the same results (and allow the alarm to be heard)
the volume of the audio signal would have to be turned down
drastically. Thus, selective frequency attenuation is an improved
option compared to channel volume attenuation.
[0007] In some embodiments, the system and method determine
direction data that includes information about from which direction
the alarm is coming. This direction data can be used to selectively
attenuate certain channels (or speakers) of the audio signal. For
example, if the alarm signal is coming from the left rear of the
automobile, then the system and method can attenuate the alarm
frequency in those left rear speakers to allow the alarm signal to
be detected. In some embodiments the channels of the audio signal
may be attenuated through a proportional ratio based do the
direction from where the siren or alarm signal is coming. Moreover,
the direction can be defined using a grid having defined
coordinates and centered on the vehicle. In addition, the direction
data can include an angle relative to a reference line on the
vehicle corresponding to a direction from which the audio emergency
warning signal is being emitted.
[0008] Some embodiments of the system and method generate
multi-channel attenuation coefficients and use these coefficients
to selectively attenuate amplitude of at least some channels of the
audio signal. These multi-channel attenuation coefficients are
obtained from an overall power level of the audio signal, an alarm
frequency of the alarm signal, and the direction data. In addition,
a filter can be generated using the coefficients and then used to
selectively attenuate at least some channels in the audio signal.
Moreover scale factors can be determined using the direction data
and used to scale the amplitude. The amplitude of at least some of
the plurality of channels also can be scaled based on the overall
power level and the scale factors. In other embodiments, the system
and method avoid attenuating any of the plurality of channels that
contain a vocal track in order to maintain the integrity of music
contained in the audio signal.
[0009] In some embodiments of the system and method duration is
specified during which the multi-channel coefficients are applied
to the audio signal. Once the duration has elapsed or the alarm
signal ceases the amplitude is returned to prior levels. Moreover,
the alarm signal may be captured by one or more microphone external
to the vehicle for reproduction with the audio signal. In other
words, the alarm signal can be played through the plurality of
channels (or speakers) to alert the listener to the alarm signal.
In other embodiments, one or more audio cues (or earcons) are
played for the listener in order to alert the listener to the alarm
signal.
[0010] The rate of occurrence of the audio cue as well as it
amplitude can be based on one or more of a distance of the alarm
from the vehicle, the speed at which the alarm is moving toward the
vehicle, and the type of alarm (such as a fire, police, or
ambulance siren). Specifically, in some embodiments the system and
method estimate a distance between the source of the audio
emergency warning signal and the vehicle and a rate of occurrence
and amplitude of the playing of audio cues is based on the
distance. In other embodiments the system and method estimate a
speed between the source of the audio emergency warning signal and
the vehicle and a rate of occurrence and amplitude of the playing
of audio cues is based on the speed. In still other embodiments the
system and method estimate a type of alarm based on the alarm
frequency of the audio emergency warning signal. The rate of
occurrence and amplitude of the playing of audio cues is based on
the type of alarm.
[0011] It should be noted that alternative embodiments are
possible, and steps and elements discussed herein may be changed,
added, or eliminated, depending on the particular embodiment. These
alternative embodiments include alternative steps and alternative
elements that may be used, and structural changes that may be made,
without departing from the scope of the invention.
DRAWINGS DESCRIPTION
[0012] Referring now to the drawings in which like reference
numbers represent corresponding parts throughout:
[0013] FIG. 1 is block diagram of an exemplary embodiment of the
audio signal attenuation system and method described herein.
[0014] FIG. 2 is a detailed block diagram illustrating a specific
embodiment of the audio signal attenuation system and method shown
in FIG. 1.
[0015] FIGS. 3A and 3B are a flowchart diagram illustrating an
overview of the operation of the audio signal attenuation system
shown in FIGS. 1 and 2.
[0016] FIG. 4 is a flowchart diagram illustrating the detailed
operation of selective frequency attenuation in the audio signal
attenuation system shown in FIGS. 1-3.
[0017] FIGS. 5A and 5B are a flowchart diagram illustrating the
detailed operation of using direction data to selectively attenuate
channels as used in the audio signal attenuation system shown in
FIGS. 1-3.
DETAILED DESCRIPTION
[0018] In the following description of an audio signal attenuation
system and method reference is made to the accompanying drawings,
which form a part thereof, and in which is shown by way of
illustration a specific example whereby embodiments of the audio
signal attenuation system and method may be practiced. It is to be
understood that other embodiments may be utilized and structural
changes may be made without departing from the scope of the claimed
subject matter.
[0019] Moreover, in the following description numerous specific
details are set forth. However, it is understood that embodiments
of the audio signal attenuation system and method may be practiced
without these specific details. In other instances, well-known
circuits, structures, and techniques have not been shown in order
not to obscure the understanding of this description.
[0020] Embodiment of the audio signal attenuation system and method
may be implemented by hardware, firmware, software or any
combination thereof. When implemented in software, embodiments of
the audio signal attenuation system and method are essentially the
code segments to perform the necessary tasks. The software may
include the actual code to carry out the operations described in
some embodiments, or code that emulates or simulates the
operations.
[0021] The program or code segments can be stored in a processor or
machine accessible medium or transmitted by a computer data signal
embodied in a carrier wave, or a signal modulated by a carrier,
over a transmission medium. The "processor readable or accessible
medium" or "machine readable or accessible medium" may include any
medium that can store, transmit, or transfer information. Examples
of the processor readable medium include an electronic circuit, a
semiconductor memory device, a read only memory (ROM), a flash
memory, an erasable ROM (EROM), a floppy diskette, a compact disk
(CD) ROM, an optical disk, a hard disk, a fiber optic medium, a
radio frequency (RF) link, etc. The computer data signal may
include any signal that can propagate over a transmission medium
such as electronic network channels, optical fibers, air,
electromagnetic, RF links, etc. The code segments may be downloaded
via computer networks such as the Internet, Intranet, and so
forth.
[0022] The machine accessible medium may be embodied in an article
of manufacture. The machine accessible medium may include data
that, when accessed by a machine, cause the machine to perform the
operation described herein. The term "data" here refers to any type
of information that is encoded for machine-readable purposes.
Therefore, it may include program, code, data, file, and so
forth.
[0023] Each or some embodiments of the audio signal attenuation
system and method may be implemented by software. The software may
have several modules coupled to each another. A software module is
coupled to another module to receive variables, parameters,
arguments, pointers, etc. and/or to generate or pass results,
updated variables, pointers, and so forth. A software module may
also be a software driver or interface to interact with the
operating system running on the platform. A software module may
also be a hardware driver to configure, set up, initialize, send
and receive data to and from a hardware device.
[0024] Some embodiments of the audio signal attenuation system and
method may be described as a process which is may be depicted as a
flowchart, a flow diagram, a structure diagram, or a block diagram.
Although a block diagram may describe the operations as a
sequential process, many of the operations can be performed in
parallel or concurrently. In addition, the order of the operations
may be re-arranged. A process is terminated when its operations are
completed. A process may correspond to a method, a program, a
procedure, and so forth.
[0025] It should be noted that embodiments of the audio signal
attenuation system and method may be implemented in hardware,
firmware, or software, or any combination thereof. Moreover,
various processing components described below may be software
components or modules associated with a processor (such as a
central processing unit). In addition, audio "signals" and
"sub-signals" represent a tangible physical phenomenon,
specifically, a sound, that has been converted into an electronic
signal and suitably pre-processed.
[0026] All or some embodiments of the audio signal attenuation
system and method may be employed in a conventional vehicle. A
conventional vehicle includes a standard audio system having at
least two channels which are reproduced through speakers. However,
embodiments of the audio signal attenuation system and method may
be implemented on any vehicle having any number of speakers and
channels.
I. Audio Signal Attenuation System
[0027] FIG. 1 is block diagram of an exemplary embodiment of the
audio signal attenuation system and method described herein.
Referring to FIG. 1, the audio signal attenuation system 10 is
illustrated. The system 10 receives an audio emergency warning
signal 12, which may be any audible emergency warning signal. By
way of example, this audio emergency warning signal 12 may be a
siren from an emergency response vehicle. The audio emergency
warning signal 12 is received by the system 10 through sensors such
as microphones or microphone arrays (not shown).
[0028] Once the audio emergency warning signal 12 is received by
the system 10 it is converted into the frequency domain.
Conventional methods to convert a signal into the frequency domain
may be employed, such as a Fast Fourier Transform or a Modified
Discrete Cosine Transform. Once converted into the frequency
domain, a frequency analysis module 14 performs a frequency
analysis on the audio emergency warning signal 12 to generate alarm
frequency characteristics 15.
[0029] The alarm frequency characteristics 15 are used to derive a
filter (not shown) for filtering an alarm frequency from an audio
signal 20. It should be noted that the audio signal 20 is typically
playing inside a vehicle, such as an automobile. The alarm
frequency is the dominant or fundamental frequency of the audio
emergency warning signal 12. Masking techniques are used to filter
or remove the alarm frequency from the audio signal 20. The alarm
frequency is obtained by analyzing the audio emergency warning
signal 12 in the frequency domain and comparing it against a set
threshold. Subsequently, the fundamental frequency, F.sub.0, of the
dominant peaks is computed. Finally, the filter is designed based
on this analysis.
[0030] As shown in FIG. 1, a direction data 16 represents data that
indicates a direction from where the audio emergency warning signal
12 is being emitted. The direction data 16 may be detected by at
least one sensor strategically placed around the body of the
vehicle. The vehicle may be represented as a grid having defined
coordinates, whereby the strategic placement of the sensors
captures the directional angle from where the audio emergency
warning signal 12 is being detected in relation to the vehicle. By
way of example, if the audio emergency warning signal 12 is being
received by sensors on the right side of the vehicle, the direction
data 16 includes data illustrating that the source of the audio
emergency warning signal 12 is being emitted (or emanates) from the
right side of the vehicle.
[0031] In some embodiments, multi-channel attenuation coefficients
18 are generated using the alarm frequency characteristics 15 (or
the alarm frequency), an overall power level 21 (or amplitude) of
the audio signal 20, and the direction data 16. In some embodiments
the direction data 16 is analyzed to determine scale factors (not
shown) for scaling the amplitude of the audio signal 20 based on
the direction from where the audio emergency warning signal 12 is
being detected. In some embodiments the audio signal 20 is played
back in a listening environment that is the interior of a vehicle
(such as an automobile). In some embodiments include detecting a
direction relative to the vehicle from where the audio emergency
warning signal 12 is being emitted to generate the direction data
16. Moreover, in some embodiments the direction data 16 includes an
angle relative to a reference line on the vehicle corresponding to
a direction from where the audio emergency warning signal 12 is
being emitted.
[0032] Embodiments of the audio signal attenuation system 10 and
method include a power analysis module 22 that analyzes the overall
power lever (loudness or amplitude) of the audio signal 20. This
analysis may occur through strategic placement of sensors within
the body of the vehicle. Alternatively, the overall power level
information may be passed from an internal audio system to
embodiments of the audio signal attenuation module 10. In alternate
embodiments, visual data (Vdata) 23 from the power analysis module
22 may be used to visually display the overall power level of the
audio signal 20.
[0033] In some embodiments the audio signal 20 contains a plurality
of channels. Typically, each channel is played back through a
speaker in the vehicle. The multi-channel attenuation coefficients
18 may also be used to determine filters for filtering the audio
signal 20 based on the alarm frequency and scale factors for
scaling the amplitude of the audio signal 20 are determined using
the direction data 16. From the multi-channel attenuation
coefficients 18, the alarm frequency of the audio emergency warning
signal 12 is filtered from the audio signal 20 in some or all of
the channels proportionately, based on the direction data 16.
[0034] In some embodiments the direction data 16 is used to
identify the channel (or speaker) having the greatest impact. The
direction data 16 is analyzed to determine scale factors for
scaling the amplitude of at least some of the plurality of channels
based on the direction from where the audio emergency warning
signal 12 is being detected. Thus, the audio signal 20 is filter to
attenuate or completely remove the alarm frequencies. In other
words, the audio signal 20 is scaled to lower the amplitude of the
audio signal in at least some of the channels. This selectively
mutes the audio signal 20 so that the audio emergency warning
signal 12 can be detected (such as by a listener in the vehicle
listening to the audio signal).
[0035] Each channel (or speaker) may be scaled according to a
ratio, or be proportionately attenuation based on the direction of
the audio emergency warning signal 12 such that the channels having
the greatest impact are attenuated to a greater degree than other
channels. For example, if the audio emergency warning signal 12 is
being detected from the right side of the vehicle, the amplitude of
the front right and rear right speakers may be scaled to a greater
degree than the front left and rear left speakers. In some
embodiments, channels in the audio signal 20 that contain vocal
tracks may not be filtered or may be minimally filtered in order to
maintain the integrity of the music in the audio signal 20. In
other embodiments, the amplitude of all channels may be scaled.
[0036] Once the multi-channel attenuation coefficients 18 and scale
factors are determined, an attack/release (or duration) schedule 26
for their application is determined. Specifically the duration for
the application of the multi-channel attenuation coefficients is
determined such that the filtered and scaled audio signal 20 is
returned to normal levels once the audio emergency warning signal
12 has ceased or gets far enough away from the vehicle. A
multi-channel attenuator 28 is used to apply the multi-channel
attenuation coefficients and scale factors to the audio signal 20.
The band (or channel) attenuated multi-channel audio output 30 is
output from the multi-channel attenuator 28.
[0037] In some embodiments, the audio emergency warning signal 12
may be synthesized or passed through for playback over the speakers
in the vehicle. In this embodiment, a multi-channel panner 34 is
used to allow the audio emergency warning signal 12 to be
reproduced through the internal audio speakers (or channels)
according to the direction data 16. The output from the
multi-channel panner 34 is a panned multi-channel emergency warning
signal (or alarm) 36. The band-attenuated multi-channel audio
output 30 is added to the panned multi-channel emergency warning
signal 36 using an adder 38 to produce an output of multi-channel
pulse-code modulation (PCM) audio 40.
[0038] FIG. 2 is a detailed block diagram illustrating a specific
embodiment of the audio signal attenuation system and method shown
in FIG. 1. In particular, FIG. 2 illustrates the audio signal
attenuation system 10 and method having an upmixer 100 to allow a
stereo audio signal 105 input to be upmixed into a 5.1 audio signal
110. It should be noted that although in this example the stereo
audio signal 105 is upmixed to the 5.1 audio signal 110, in other
embodiments the upmix may be a mono to stereo audio signal or a 5.1
to 7.1 audio signal. Moreover, in the embodiments shown in FIG. 2,
the upmixer 100 uses the Neo:X.TM. technology to create the 5.1
audio signal 110. The Neo:X.TM. technology is made by DTS.RTM.,
Inc. of Calabasas, Calif.
[0039] The audio attenuation system 10 and method also include the
multi-channel attenuator 28 that is used to apply the multi-channel
attenuation coefficients and scale factors to the 5.1 audio signal
110. The multi-channel attenuator 28 includes a multi-channel band
selective filter 115 that selectively filters a frequency or
frequencies from the 5.1 audio signal 110. Moreover, the
multi-channel attenuator 28 includes a multi-channel amplitude
scaling module 120 that scales the various channels of the 5.1
audio signal 110 based on the scale factors and direction data 16.
The multi-channel attenuator 28 also includes a head-related
transfer function (HTRF) based filter 125 for tuning the 5.1 audio
signal to a listener's head and the listening environment. In some
embodiments the listening environment is within a vehicle, such as
an automobile.
[0040] The audio emergency warning signal 12 is input to the
frequency analysis module 14 that processes the signal 12 and
outputs alarm frequency characteristics 15. Moreover, the 5.1 audio
signal 110 is processed by the power analysis module 22 to obtain
the overall power level 21 of the 5.1 audio signal 110. The
multi-channel attenuation coefficients 18 are generated using the
overall power level 21, the direction data 16, and the alarm
frequency characteristics 15. The multi-channel attenuation
coefficients 18 includes multi-channel filter coefficients 130,
which are by the multi-channel band selective filter 115 to filter
certain frequencies (such as the frequency of the audio emergency
warning signal 12) out of the 5.1 audio signal 110. Moreover, the
multi-channel attenuation coefficients 18 include multi-channel
amplitude scale factors (or scale factors) 135, which are used by
the multi-channel amplitude scaling module 120 to scale at some of
a plurality of channels of the 5.1 audio signal 110 based on the
direction of the audio emergency warning signal 12 and the overall
power level 21 of the 5.1 audio signal 12.
[0041] In the embodiments shown in FIG. 2, the audio signal
attenuation system 10 and method includes the multi-channel panner
34 that is used to reproduce or synthesize the audio emergency
warning signal 12 through the internal audio speakers (or
channels). In some embodiments the multi-channel panner 34 uses the
direction data 16 to determine how the audio emergency warning
signal 12 should be played back through the audio speakers and
which speaker should be used.
[0042] In some embodiments an earcon 140 is also used by the
multi-channel panner 34 to introduce audio cues into the listening
environment. The earcon 140 can be a single one or a series of
brief, distinctive sounds that are used to convey information to a
listener in the listening environment. In some embodiments the
earcon 140 may be used in conjunction with the playing of the audio
emergency warning signal 12, while in alternative embodiments the
earcon 140 may be used alone.
[0043] In some embodiments the rate of occurrence (or how often the
audio cue is played) and the amplitude of the playing of audio cues
is based on the distance between the source of the audio emergency
warning signal 12 and the vehicle containing the listening
environment. In other embodiments the rate of occurrence and
amplitude of the audio cues is based on a speed between the source
of the audio emergency warning signal 12 and the vehicle. In still
other embodiments the rate of occurrence and amplitude of the audio
cues is based on the type of alarm, which may be determined by the
frequency and other attributes of the audio emergency warning
signal 12.
[0044] The output from the multi-channel panner 34 is a panned
multi-channel warning signal 145. A band-attenuated 5.1 audio
signal 150 is output from the multi-channel attenuator 28. The
panned multi-channel warning signal 145 and the band-attenuated 5.1
audio signal 150 are added to each other using the adder 38 to
produce an output of the multi-channel pulse-code modulation (PCM)
audio 40.
II. Operational Overview
[0045] FIGS. 3A and 3B are a flowchart diagram illustrating an
overview of the operation of the audio signal attenuation system 10
shown in FIGS. 1 and 2. In should be noted that although the
following flowcharts may illustrate an operation or occurring in a
serial manner, in some embodiments it is possible that the
operation occurs in a parallel manner. The operation begins by
receiving as input an audio emergency warning signal 12 (box 300).
This audio emergency warning signal 12 may be a siren or alarm from
an emergency vehicle, such as an ambulance or police car. The input
into the system 10 is typically achieved by using at least one
microphone situated around a vehicle in which the audio signal 10
is playing. Embodiments of the system 10 also receive as input an
audio signal 20 that is being played back in the vehicle (box
305).
[0046] Embodiments of the system 10 determine an overall power
level 21 of the audio signal 20 (box 310). The audio emergency
warning signal 12 is converted in to the frequency domain and an
alarm frequency of the signal 12 is determined by the system 10
(box 315). Embodiments of the system 10 also determine direction
data 16 by analyzing the alarm frequency and amplitudes from a
microphone array (box 320). This direction data 16 determines a
direction relative to the vehicle from which the audio emergency
warning signal 12 is being emitted (such as an ambulance).
[0047] Embodiments of the system 10 compute multi-channel
attenuation coefficients 18 from the overall power level 21, the
direction data 16, and the alarm frequency (box 325). These
coefficients 18 are used to selectively attenuate an amplitude of
at least some channels of the audio signal 20 (box 330). Moreover,
the coefficients 18 are used to generate a filter (box 335), and
the filter is used to filter the audio signal 20 and attenuate the
alarm frequency in the audio signal 20 (box 340).
[0048] Embodiments of the system 10 also determine scale factors
135 using the direction data 16 (box 345). These scale factors 135
are used to scale an amplitude of at least some of the channels in
the audio signal 20 (box 350). Moreover, some embodiments of the
system 10 specify a duration for an application of the
multi-channel attenuation coefficients 18 to the audio signal 20
such that the amplitude is returned to previous levels (or the
volume of the audio signal 20 immediately prior to the detection of
the audio emergency warning signal 12) once the audio emergency
warning signal 12 ceases (box 355).
[0049] In some embodiments, the system 10 plays the audio emergency
warning signal 12 through the speakers in the vehicle. In some
embodiments, this playback is achieved by playing the audio
emergency warning signal 12 through each of the plurality of
channels (or speakers) (box 360). In other embodiments, this
playback occurs only through a portion of the available channels
based on the direction data (box 365). For example, the direction
data may indicate that the audio emergency warning signal 12 is
coming from the right side of the vehicle. In this case the
playback of the signal 12 would be played back primarily through
the speakers on the right side of the vehicle.
[0050] Some embodiments of the system 10 use earcons 140 (or audio
cues) played back through the speakers to alert a listener of the
audio emergency warning signal 12. The audio cues are typically
played through each of the plurality of channels (box 370). In some
embodiments, the system 10 estimates a distance between the source
of the audio emergency warning signal 12 and the vehicle that is
playing the audio signal 20 (box 372). Based on this distance, the
rate of occurrence (or how many times per minute the audio cues are
played) and the amplitude of the audio cues are determined (box
375). In other embodiments the system 10 estimates a speed between
the source of the audio emergency warning signal 12 and the vehicle
(box 377). This gives an estimate of how fast the audio emergency
warning signal 12 is approaching the vehicle that is playing back
the audio signal 20. The rate of occurrence and amplitude of the
audio cue is based on the speed (box 380). In some embodiments the
system 10 estimate the type of alarm based on the frequency or
frequencies of the audio emergency warning signal 12 (box 382), and
the audio cues are played based on the type of alarm (box 385). For
example, if the system 10 detects from the frequency that the alarm
is from a police car, the audio cue may alert the listener in a
manner that sounds different from an audio cue when the alarm is
from an ambulance. The processed audio signal is output from
embodiments of the system 10 as a multi-channel pulse-code
modulation (PCM) audio signal (box 390).
III. Operational Details
[0051] FIG. 4 is a flowchart diagram illustrating the detailed
operation of selective frequency attenuation as used in the audio
signal attenuation system 10 shown in FIGS. 1-3. The operation
begins by receiving as input the audio emergency warning signal 12
(box 400). Next, the audio emergency warning signal 12 is converted
into the frequency domain (box 405). Embodiments of the system 10
then analyze the signal 12 in the frequency domain to obtain alarm
frequency characteristics 18 (box 410). A filter 130 then is
derived using the alarm frequency characteristics 18 (box 415). The
filter 130 can be used to filter the alarm frequency from the audio
signal 20 and selectively attenuate the alarm frequency in the
audio signal 20.
[0052] Embodiments of the system 10 compare the alarm frequency
characteristics 18 to a set threshold (box 420). Dominant peaks are
defined as those parts of the audio signal 20 that are above the
set threshold. Embodiments of the system 10 then compute a
fundamental frequency of the dominant peaks, where the fundamental
frequency is also known as the alarm frequency, or the frequency of
the audio emergency warning signal 12 (box 425).
[0053] Embodiments of the system 10 selectively attenuate a
specific frequency in the audio signal 20 such that an amplitude of
the specific frequency is attenuated relative to other frequencies
in the audio signal 20 (box 430). In some embodiments the specific
frequency corresponds to the alarm frequency of the audio emergency
warning signal 12. In other words, the frequency (or at least the
dominant or fundamental frequency) of an alarm is attenuated
markedly as compared to the other frequencies in the audio signal
20. In some embodiments, the system 10 attenuates the alarm
frequency to zero such that the alarm frequency is completely
removed from the audio signal 20 (box 435). Note that this is an
optional step as indicated by the dashed line.
[0054] Some embodiments of the system 10 selectively attenuate the
alarm frequency for each channel of a multi-channel audio signal 20
(box 440). It is much more effective to attenuated all channels to
allow the listener to effective hear the audio emergency warning
signal 12 outside of the vehicle. In other embodiments a
low-frequency effects (LFE) channel of the audio signal 20 is
attenuated along with any other channels (box 445). Attenuating the
LFE channel be even a few decibels serves to improve detection of
the audio emergency warning signal 12. This is because it is easier
for the mind to focus on the signal 12 when the LFE channel is
attenuated. This is especially true because the level of the LFE
channel is often quite high in automobiles.
[0055] In some embodiments the system 10 attenuates the front
channels of the audio signal 10 more than the other channels (box
450). This makes it easier for the listener to hear the audio
emergency warning signal 12 because the listener perceives the
front channels as stronger than the other channels. Embodiments of
the system 10 output the processed audio signal as a
band-attenuated multi-channel PCM audio signal (box 455).
[0056] FIGS. 5A and 5B are a flowchart diagram illustrating the
detailed operation of using the direction data 16 to selectively
attenuate channels as used in embodiments of the audio signal
attenuation system 10 shown in FIGS. 1-3. The operation begins by
receiving an input the audio emergency warning signal 12, where the
signal 12 is external to a listening environment of an audio signal
20 (box 500). In addition, the system 10 receives as input the
audio signal 20 having a plurality of channels (box 505).
[0057] Embodiments of the system 10 selectively attenuate an
amplitude of at least some of the channels of the audio signal 20
based on a direction of the audio emergency warning signal 12 (box
510). In some embodiments the listening environment is the interior
of a vehicle (box 515). This means that the audio signal 20 is
playing within the vehicle.
[0058] The system 10 detects a direction relative to a source from
which the audio emergency warning signal 12 is being emitted in
order to obtain direction data 16 (box 520). In some embodiments a
grid is used that has defined coordinates and is centered on the
vehicle having the listening environment (box 525). The direction
data 16 may include an angle relative to a reference line that is
centered on the vehicle (box 530). This angle corresponds to a
direction from where the audio emergency warning signal is being
emitted.
[0059] The direction data 16 is processed to determine an amplitude
of the audio emergency warning signal 12 as a function of direction
(box 535). In this manner the audio emergency warning signal 12 can
be localized and its direction determined. The system 10
selectively attenuates an amplitude of at least some channels of
the audio signal 20 based on the amplitude of the audio emergency
warning signal 12 as a function of direction (box 540).
[0060] Embodiments of the system 10 also analyze the direction data
16 to determine scale factors for scaling the amplitude of at least
some channel of the audio signal 20 based on the direction relative
to the source from where the audio emergency warning signal is be
emitted (box 545). The scale factors are used to selectively
attenuate the amplitude of at least some of the plurality of
channels of the audio signal 20.
[0061] The audio emergency warning signal 12 is analyzed by the
system 10 to obtain alarm frequency characteristics 18 (box 555). A
filter is derived by using the alarm frequency characteristics 18
(box 560), and the audio signal 20 is filtered using the filter and
the scale factors to selectively attenuate the alarm frequency in
the audio signal 20 in at least some of the plurality of channels
(box 565). In addition, some embodiments of the system 10 scale the
amplitude of at least some of the channels such that those channels
in a direction relative to the source from where the audio
emergency warning signal 12 is emanating are scaled to a lower
amplitude than other channels (box 570).
[0062] In some embodiments an overall power level 21 of the audio
signal 20 is determined (box 575) and the amplitude of at least
some channels is scaled based on the overall power level 21 and the
scale factors 135 (box 580). In some embodiments of the system 10,
any channels containing a vocal track are not attenuated (box 585).
The output is the process audio signal as an amplitude-scaled
multi-channel PCM audio signal (box 590).
[0063] There have been described systems techniques for detecting
an external audio emergency warning signal in a listening
environment when an audio signal is playing in the listening
environment. Moreover, although the subject matter has been
described in language specific to structural features and/or
methodological acts, it is to be understood that the subject matter
defined in the appended claims is not necessarily limited to the
specific features or acts described above. Rather, the specific
features and acts described above are disclosed as example forms of
implementing the claims.
* * * * *